The invention relates to a wheel of a motor vehicle having a hub portion, spokes extending radially outwards from the hub portion and a rim which is supported on the spokes, as well as a spoke area cover which is delimited by the rim. With regard to prior art, reference is made, for example, to DE 10 2009 024 792 A1.
Cover plates or cover elements for automotive wheels, which are colloquially referred to as rims, are known in various embodiments. Such a cover plate, as is proposed in the aforementioned document as a “rim” (which actually only covers the annular area containing the spokes between the hub portion and the actual rim on which a wheel tire is mounted), is presently designated as a spoke area cover. The spoke area of the annular area is between the hub portion and the rim. In the prior art according to the cited document, the cover is provided on the interior side of the spokes (in a mounted state on the vehicle), in order to at least reduce the impingement on the spokes of wear debris from the friction brake of the vehicle located in the so-called rim bowl. This cover (or this covering element) is made of plastic, in particular polycarbonate.
In principle, a known cover fulfills the above-mentioned requirement, however further requirements are placed on vehicle wheels and thereby also on those with spokes, which may advantageously be designed in a lightweight construction in particular through the use of suitable materials, said requirements here regarding the greatest possible minimization of the air resistance coefficient of the motor vehicle.
The object of the present invention is to provide a measure to minimize the air resistance coefficient of the motor vehicle.
This and other objects are achieved by a wheel of a motor vehicle, comprising a hub portion, spokes extending radially outwards from the hub portion, a rim which is supported on the spokes, and a spoke area cover which is delimited by the rim, wherein a respective cover is provided on both sides of the spokes, i.e. facing the interior side of the spokes and facing the exterior side of the spokes.
In that a spoke area cover between the hub portion and the rim which extends at least between the rim and the hub portion is provided not only on the side of the wheel facing the interior side of the spokes (in an installed state of the wheel on the vehicle), but also on the side of the wheel facing the exterior side of the spokes (in an installed state of the wheel on the vehicle), air vortexes which would form on the spokes during driving of the vehicle without such a cover are avoided. This results in a reduced air resistance of the vehicle. Here, the cover which covers the annular area in which the spokes are located (=“spoke area”) on both sides comprises a “continuous” or smooth surface, i.e. any cross sections which are made through this cover should not comprise any abrupt changes in course, so that while driving the vehicle, an airflow which is as low-loss as possible can be formed on the surface thereof.
If the interior-side cover, which is annular when seen in a projection in the direction of the wheel rotational axis, is adhered to the edge of the hub portion and to an annular region of the rim and/or the interior side of the spokes, a secure seal against the entry of brake wear debris or other dust or dirt particles into the spoke area is thus ensured in this location. Advantageously, this connection technique of adhesion is also simple to represent, wherein the cover may be designed in plastic analogous to the known prior art, but may also comprise other suitable materials.
The exterior-side cover may be designed as a complete surface, i.e. extending completely within the rim or, like the interior-side cover, the exterior-side cover may be designed in an annular manner when seen in a projection in the direction of the wheel rotational axis and thus extend between the rim and the hub portion of the wheel. The exterior-side cover is preferably interchangeably mounted on the wheel (in case of optical damage), and its edge can be inserted for this purpose into a groove in an annular rim region (in the former case of a complete surface cover) or (in the latter case of an annular cover) its two edges can be inserted in grooves or the like in an annular region of the rim and in the hub portion.
The spoke area is thus substantially sealed off from the environment by use of the interior-side and exterior-side covers, so that an undesired entry of dirt into the spoke area is substantially excluded. However, due in particular to the interchangeability of the exterior-side cover, a 100% exclusion or seal cannot be guaranteed. In order to avoid the formation of overpressure or underpressure in the spoke area (caused by temperature influences such as sunlight or brake heat and/or airflow conditions at higher driving speeds of a vehicle equipped with a wheel according to the invention), at least one overpressure-dependent and/or underpressure-dependent ventilation opening for the spoke area closed from the environment by way of the covers may be provided either in the hub portion of the wheel or in one of the covers, preferably in the interior-side cover. In order to prevent as far as possible the simultaneous entry of dirt particles in the event of an entry of air into the spoke area caused by underpressure, a suitable air filter element may be provided on the aforementioned ventilation opening. In this case, a single ventilation opening may be provided both for supply and removal of air from the spoke area, alternatively however there may be provided here different ventilation openings.
In order to allow a filling with air (or another gas) of the pneumatic tire fitted to the rim of a wheel according to the invention, a preferably sealingly closeable access opening to an air valve provided in the rim for filling the pneumatic tire may be provided in the exterior-side cover. Alternatively, a central valve may be provided in the hub portion of the wheel, to which is connected a line for the filling of the pneumatic tire which extends inside the wheel, for example in a spoke.
To enable, for example, a visual inspection of the spoke area, for instance for checking the safe function of an aforementioned air filter element on a ventilation opening, the exterior-side cover may be formed in a transparent plastic. This advantageously also results due to the visibility of the spokes in a pleasant visual appearance of a wheel according to the invention.
An advantageous arrangement of a wheel according to the invention on a wheel carrier of a two-track motor vehicle arises along with a wheel brake arranged as usual in the wheel bowl if a cover plate is mounted on the wheel carrier in a somewhat fixed fashion to the vehicle as the air resistance caused by the wheel may hereby be further reduced, particularly at higher driving speeds of the vehicle. The edge of the cover plate lies preferably in the area of the inner rim flange. The wheel bowl is the known, nearly circular cylindrical “cavity” located on the inner side behind the spokes of conventional motor vehicle wheels—delimited by the rim. In order, if necessary, to allow a sufficient cooling of the wheel brake, which is embodied as usual as a friction brake, a supply opening for cooling air and a discharge opening for the supplied cooling air directed toward the friction brake may be provided in the cover plate.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.